Palynological and paleoecological assessment of a Pennsylvanian shale overlying the Danville coal member (VII) in Sullivan County, Indiana

Abstract:

Shale samples from three Upper Pennsylvanian assemblages overlying the Danville (No. 7) Coal Member in Sullivan County, Indiana were compared with respect to miospore content. Eight samples from each of the Hawthorn, Dugger and Minnehaha mines were chemically macerated and analyzed for pollen/spore content. A total of 108 species assigned to 40 genera were recovered. A comparison of the palynoflora from the three assemblages reveals 17 genera and 32 species found in common. The palynoflora is dominated by the following four genera: Lycospora, Laevigatosporites. Punctatisporites and Punctatosporites. Genera of secondary importance include: Spinosporites, Crassispora, Calamospora, Latosporites, Cycloqranisporitesand Thymospora. These findings are similar to other palynofloras of comparable age from the United States and Europe.Abundance data at each site from the three localities were analyzed using cluster analysis. This was achieved employing the Baroni-Urboni-Buser correlation coefficient (complete linkage, furthest neighbor strategy). This method uses presence-absence data to indicate association between sites. Results revealed few taxonomic differences within or between mines. The uniformity in palynoflora observed between all sites is indicative of contemporaneous deposition which represents a regional flora. Percentage of miospore components assigned to previously established plant affinities were arranged by major plant groups. This allowed indirect comparison with megaflora from the same area as reported by Pheifer (1979). Results were found to be complementary and corroborative. Data from the three mines revealed an abundance of arborescent lycopods, ferns and sphenopsids with few gymnosperms. This is suggestive of current paleoenvironmental models which indicate a wet swamp regime.It is likely that the three areas in this study represent a small portion of a vast freshwater swamp located on the eastern periphery of the Illinois Coal Basin. This interpretation is substantiated by species composition, uniformity in palynoflora and absence of species associated with saline environments.